


Open up, enlighten me

by EnlacingLines



Category: Fire Emblem: Fuukasetsugetsu | Fire Emblem: Three Houses
Genre: Alternate Universe - College/University, Alternate Universe - Modern Setting, Anal Fingering, Blow Jobs, Childhood Friends, Cute, Established Relationship, Hand Jobs, M/M, Sylvain is smart and Felix likes it
Language: English
Status: Completed
Published: 2020-05-09
Updated: 2020-05-09
Packaged: 2021-03-03 02:40:46
Rating: Explicit
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 9,303
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/24097471
Author URL: https://archiveofourown.org/users/EnlacingLines/pseuds/EnlacingLines
Summary: So. He has a thing for Sylvain being… smart. Or talking about his niche interests. Felix groans and covers his eyes. That’s weird. Not the weirdest thing he could like, but it’s still… hard to explain. And also clearly inconvenient, as proven just now.Sylvain is smart, and Felix is weak. He couldn't be more annoyed about it.
Relationships: Felix Hugo Fraldarius/Sylvain Jose Gautier
Comments: 26
Kudos: 306





	Open up, enlighten me

**Author's Note:**

> My love of smart Sylvain is clearly out of control. 
> 
> Title from After Forever's Energise Me.
> 
> All the thanks to my wonderful beta Valania, who is so fantastic for supporting this from start to finish. 
> 
> Enjoy reading!

Sylvain has always been intelligent. It’s one of the aspects Felix has always found both infuriating and enticing; mainly due to how it’s always drawn him to Sylvain in different ways throughout his life. 

When they were younger, those two years of difference seemed like a chasm of knowledge Felix could barely dip his toe into, although back then, Sylvain was most likely operating at a level far higher than that. He read real books; thick ones without pictures that Felix struggled to hold, let along decipher. 

What’s more, he just _knew_ things. Could tell Felix the names of every bug Ingrid found, why the tide changed when they visited the beach, and which snow would make the best arsenal for their battles. Felix always wanted to know; Glenn would tell him things for a while, but then get bored, tell Felix to stop asking questions. His father was never around, Dimitri never knew anything, Ingrid knew very specific facts about horses and tree climbing, neither of which he wanted to know. 

But Sylvain though, knew _everything_. And thus became the first manifestation of Felix’s curiosity towards him, in which he followed Sylvain around for as long as he could, asking questions. Sylvain would always answer, and in fact was happy to answer; he almost couldn’t stop giving information. Not in an arrogant manner, like some of Felix’s classmates, but with joy and a smile; as if giving Felix an answer or knowledge was the best gift he could bring. 

And it was, in Felix’s mind. Sylvain always jumped at the idea of learning something new, inspiring Felix to do the same. He read more books in the summers they shared together than any other time, just to try and gain a glimpse into what Sylvain experienced by knowing and understanding. 

Felix always spent his time running to catch people; running to catch Dimitri, who was so much faster. To catch Ingrid, who had no time for his lack of enthusiasm to jump in mud. After Glenn, who was his hero, who he wished to be but could not quite emulate. 

To Sylvain, the fountain of all knowledge. But Sylvain was the only one who would stop and wait for him to be within arms reach. Who was happy to explain, to talk, to show Felix what he knew so he could be included. The most included Felix had, so far, ever felt. 

“Did you know,” Sylvain would start, before launching into an account of his latest topic of fascination, Felix clinging on to every word, absorbing as much information as he could. 

The others didn’t seem to enjoy it as much, but mostly as they preferred running around and making up games which Felix always seemed to be too small or too fragile to join in, their rules excluding him only in their stubbornness to play in their own way. 

Sylvain though, was content to play with Felix, and even managed to wrangle him into games all three could play. What’s more, if he didn’t know the answer, he found it, as if those huge books of his could contain the secrets of the universe if Felix was only able to phrase it correctly. For each day when Felix asks something unknown, the next brings Sylvain with the answer, and Felix can’t help but be enthralled by this person who lives to impart knowledge, and has it in abundance. 

Until it stopped. 

Looking back, Felix estimates he must have been about ten years old when Sylvain ceased to tell him new pieces of information. Perhaps it began slowly; it’s hard now, so far in the future, to recall each day, but he remembers clearly, Sylvain at ten, teaching him the names of all the flowers in his garden, yet at twelve, he claimed to not remember them. 

“It doesn't really matter what they’re called, Felix. It matters if they’re pretty,” he’d said, with a laugh that sounded like an echo of reality even back then. 

“What?” Felix had said, utterly confused by this shift. 

“You give the pretty ones to girls, Felix. That’s what flowers are for!” 

And this began Sylvain’s rhetoric that would persist for their entire adolescence. Not that Felix would hear it that often, for they end up going their separate ways until their late teens. He doesn’t see Sylvain for almost five years at one point, but he never truly forgets. Their fathers are still friends, and although Sylvain lives in a different city, he sees snatches of his life online. 

A lot of girls. A lot of dates, and a lot of sports. None of which Felix is particularly interested in, so it is a surprise when he bumps into Sylvain during his first few weeks of university. 

And it’s a literal bumping. Felix isn’t looking where he’s going, still lost in the unfamiliar halls of what he thinks is the languages department, head buried in the awful map he’d been given on his first day, still having no idea where he is. 

So he walks into a surprisingly firm and warm object, which after knocking him out of the map, he realises can only be a person. Felix grimaces at his shoes before looking up into an extremely familiar face. 

“Hey man, are you... wait, _Felix_?” He says, those light brown eyes Felix is explicit drawn to seeming to almost light up on recognition. 

The fizzing in his stomach is unexpected, and in truth, undesired. He isn’t a stranger to such feelings, but they are usually further down the line, a slow build overtime. An immediate swoop and plunge on first interaction is not something he’s experienced before. And something he’s not sure he likes. 

It is, however, Sylvain. Most undoubtedly his childhood friend, although he has changed during the intervening years. His hair is longer, curling at the edges in a way that must be precisely styled for locks to fall and wrap around one another so deliberately, working with the angles of his now wide smile. The shade is darker than Felix recalls, more burn than flame, as if age has reduced the cinders beneath. He’s tall. Frustratingly tall, as Felix always assumed their height difference was down to age, but it seems Sylvain has clawed his way into a towering presence, combined with being muscular. Nicely muscular, if the biceps appearing out of his t-shirt are any—

Felix stops his train of thought right there, mouth draining and stomach fluttering once more. He doesn’t understand quite how he’s losing his faculties so easy this morning, and over Sylvain Gautier of all people. 

“Felix? You okay, buddy?” Sylvain asks, peering down and Felix glares back. 

“Fine. Hi, Sylvain. I didn’t expect to see you here,” he says, trying for civility and ending up with something between aggravation and impatience. It happens a lot, unfortunately; there is a gap between his meaning and his actualisation in conversing. 

Sylvain laughs though, rubbing the back of his neck, a deepening of colour spreading across his cheeks that’s not quite a blush, but a highlight of near pink. It once again makes Felix’s mouth click with dryness. 

“Yeah, I transferred. So I’m actually only one year ahead of you. Didn’t expect you to be studying physics though,” he says and Felix’s eyes widen. 

“Physics. I’m in...the physics building,” he says, and swears aggressively as he holds up the map and squints. 

“Ah yeah, you are. Where are you actually trying to go?” Sylvain says, moving to stand beside Felix and stare down at the poor excuse for a map. 

Sylvain is warm. It should be impossible to tell, but Felix swears he feels his body heat filtering out and into him, which is awkward when he realises Sylvain’s been trying to explain how to get to his department for at least a minute. 

“...Just turn right at the bottom of the stairs and... you know what, let me show you,” he says suddenly, straightening up and taking the map out of Felix’s hands. 

“Wait, what—Sylvain!” he says, and Sylvain crumples it between his hands. 

“This thing is a piece of trash Felix, it’s taken you to the wrong side of campus,” Sylvain says, raising his eyebrow. 

“Don’t just throw away my things, idiot,” Felix retorts, the two moving into step easily, a little too easily in Felix’s mind. They should not still be this in synch, it’s unnatural, strange. Much like this whole encounter in itself. 

It starts from there. Initially, Felix assumes this will be the end, not for lack of wanting, but the campus is large and they both study completely different subjects. Unless the world will be obliging in frequent accidental meetings (hopefully without Felix crashing into Sylvain’s chest again), he doesn’t think they have much cause to meet again. Felix hadn’t managed to convince himself to do anything other than wave and thank Sylvain once he finds his way, but of course, he should have recalled that Sylvain is more enterprising. 

It’s less than a week later when Ingrid slams her books down on the library desk Felix has resigned himself to until he completes his essay, looking up at her slowly as she stares down, hands on her hips. 

“Were you going to tell me Sylvian is here, or just keep it a secret forever?” she says. Felix moves from annoyed to stunned, followed by that new swimming sensation which leads to his ears heating in the most frustrating way and cycles him back round to annoyance in the space of less than a few seconds. 

“You saw him?” he asks, and Ingrid nods. 

“Yeah, and he mentioned he ran into you, so I gave him your number,” she says, leaving Felix gaping. 

“You did what?” he hisses, students at other tables now staring at them in curiosity. 

Ingrid sits down and takes out her own laptop and books, not seeming to care that Felix is moving through a range of emotions; from a curling panic to a warm pleasantness, none of which he’s coping with well. 

“He said he forgot to ask you for it. I gave him mine, and Dimitri’s too. Are you really upset about it?” she asks.

Before Felix can reply, his phone, sitting next to his laptop, vibrates so hard it starts travelling across the desk, forcing him to slam his hand over it in order to keep it quiet. Ingrid raises an eyebrow. Felix flushes harder. 

“That was quick…” she mutters, giving him one last glance before opening her laptop. 

He has to restrain him from immediately looking at his phone, giving himself a stern internal lecture stating he doesn’t need to grasp for the message like a teen, doesn’t need to confirm or deny who is causing his phone to light up with such ferocity. 

He lasts ten minutes. Ingrid snorts when he succumbs. 

* * *

The three month gap which passes in between crashing into Sylvain while lost to becoming a couple is lost in a delirious haze of flirtatious words that become almost daring in their challenge, to a stumbling first date to this state of newness. Of learning, of getting lost in another person in a way Felix has not experienced before, which he’s learning is the trajectory with Sylvain. He is not so foolishly far gone to proclaim true love or soulmates, but they do work in a way he could not have anticipated. There is companionship and comfort, an ease which Felix does not find in many people naturally, and never in such a short space of time. 

It seems that Sylvain feels the same; the rush of sentiment a bubble of delightful sunlight in his veins at the knowledge. He feels it for the first time one night in Sylvain’s dorm, nestled into his chest, Sylvian’s hand running through his by now knotted hair as he speaks. 

“I wanted to study literature, but my father... well. I don’t know if you remember what he’s like. He wanted me to study Economics, so I did but I hated it. Ended up failing by not attending classes. Money can’t fix everything,” he says with a laugh, and Felix frowns, curling his hand into Sylvain’s shirt. 

“I like physics though, and maths. And he deemed it appropriate so... not literature, but this is genuinely interesting.” 

His voice transforms as he talks, and Felix tilts his head to take note of his expression as he speaks. There’s an animation to it, a new breath of life, a fastness that causes each word to blur into the next. A clear tell of excitement. 

“I’m thinking of running this side experiment, did you—” 

Sylvain pauses, Felix frowning at the suddenness, before Sylvain laughs. 

“Sorry, I’m talking your ear off. Didn’t you want to watch something?” he says, the smile on his face as he looks down so perfectly crafted, exactly equal and false, it makes his heart twist. But Sylvain is sitting up, and Felix is taken with him, still talking about a movie. Felix doesn’t know what to do, isn’t sure how Sylvain switched from being so free with his expression to shutting down, so goes on instinct. 

He reaches up, and cups Sylvain’s cheek, drawing his attention and cutting him off mid flow. Felix has no idea what words are appropriate, is not adept at encouragement or support. So he acts, and presses a kiss against Sylvain’s lips. 

It’s swift, just a brush or two, a lingering touch that has no heat or progression, but is complete in itself. He traces Sylvain’s jaw as they kiss, Sylvain meeting him the second he realises what’s happening, extending the moment by answering Felix’s kiss with his own, tilting his head for a better angle, but not delivering any further than a sweet caresses. 

“I’m glad you’re doing something you enjoy,” Felix says once they part, and Sylvain’s eyes blink several times, clearing away the remnants of affection to comprehend. Felix gets a crooked smile in return, real and theirs, a step he hopes in the right direction. 

It takes time though. In their years apart, Sylvain has developed a routine of stoppering his enthusiasm on subjects he deems unworthy to others. It makes Felix’s teeth ache with the clench of his jaw to see. It makes sense, in a terrible way, considering how he’d been so shaped by his family's hideous expectations, but convincing Sylvain that Felix wants to hear what he’s passionate about takes time. 

“What are these?” Felix says one day, as Sylvain is once again tidying his room, muttering about his housemates not doing the same with the rest of their house. 

He points to an ornate wooden box which is propped open to reveal what Felix believes are sparkling rocks. Sylvain from behind him makes a strangled noise before striding over and slamming the lid shut. 

“Nothing,” he says, not meeting Felix’s eyes, who glares and folds his arms over his chest. 

“Sylvain, I literally saw there are rocks in the box,” Felix says, tiredness slipping into his tone, and Sylvain winces, hand coming to scratch the back of his neck in nervousness. 

Felix waits, an anticipatory energy feeding his limbs, knowing he’s overstepped but backing down feels too awkward and apologising not enough. 

“They’re meteor replicas. I made them,” he says, as if he’s admitting to a felony. 

Felix is somewhat surprised at the particularity, but intrigued. 

“Show me. If you want,” he says, and although it starts at a demand, he tries to taper it into something more optional, not wanting to force but also trying to show that he wants to see if Sylvain will let him. 

The sheer surprise then clear happiness on Sylvain’s face makes Felix’s rage rise. Years of no one wanting to know about things which makes Sylvain joyful leads to him locking them up in wooden boxes, slamming lids at the slightest hint of discovery. The fact that the simple inquiry is enough to break the seal, for Sylvain quickly brings over the open box, eases the ache somewhat. At least Sylvain now feels comfortable enough to take Felix’s interest as true interest, no longer doubting. 

“I made most of these last year, I started doing some studies of meteors to fill them time, dabbling in astrophysics when I blew half my paycheck on a telescope. Anyway, I also began painting figures again, so I was in a painting mood and kinda combined it,” he says, and Felix feels an almost dizzying sensation at this new stream of information. 

Astrophysics. As a time passer. Painting figures, like the warhammer games they did as kids? The image of Sylvain hunches over a telescope and painting rocks with implicit focus and concentration is...distracting, to say the least. His energy so focused, so vibrant and overwhelming as it is now, perhaps with that way with he bites his lip, or a pencil, anything he can get his hands on as when he concentrates—

There’s a rush and a swirling, and Felix swallows as his nerves flare just slightly. He shakes his head, willing his body to calm down from strange suggestions of euphoria, as Sylvain is still speaking. He picks up one particular rock, the prettiest in Felix’s assessment. 

It’s a dark blue shade, with luminous green specks through it. Felix has to admire the patience and skill it must have taken to complete, as it looks for all his knowledge like it could be an actual meteorite rather than a creation of Sylvain’s own hand. 

“That’s a pallasite, they have green crystals inside. I think the colouring is a little off, but I got the shine pretty good. These are actually really interesting, no one is sure how they’re formed. Some think it’s by impact melting, as they’re metal and a magnesium iron-silicate, and others think they’re formed in melted asteroids,” he says, before turning back to Felix who slowly places the rock back in the box. 

“I like it,” he says thickly because he’s struck, utterly and completely, by an overwhelming feeling he understands well, even if he cannot comprehend it’s appearance now. 

Lust. 

Sylvain puts down the box, looking relaxed and content while Felix stands frozen in just how much he wants to jump his boyfriend, here and now, because he just looks like _that_. Like he’s just comfortable, at home and fully himself, using phrases and facts Felix doesn’t even fully comprehend, knowledge he’s just absorbed and can bring back at the drop of a hat. 

And because Felix is Felix, he copes with this how he copes with anything. By acting. 

The kiss is harder than Felix is aiming for, and he actually manages to trip Sylvain a little as he practically launches himself at his mouth. Their heads collide for a moment and Felix feels a sting in his lips, but he is too much powered by this sudden urge to act, to touch, to be closer than close to Sylvain. He grips his hair as an automatic response, not pulling, not yet, but just another point of contact, another place to connect. 

It doesn’t take Sylvain long to respond though, arms coming to a steadying hold around Felix's waist, returning the kiss with an enthusiasm just shy of Felix’s own. It does nothing to curb the flickers of want though, only entices and causes a swell of intensity, as his tongue curls slightly in towards the roof of Sylvain’s mouth, tasting more. 

It’s the moan which does it. Quiet, barely expressed from Sylvain, but seems to echo in Felix’s ears as their mouths switch directions, escaping as a half sign between them. In tandem, Sylvain’s hands squeeze at Felix’s waist, and he just knows it’s not enough. Not enough to curb whatever this new strange heat is between them, this match strike which has sent him so readily off kilter and hungry for the man before him. 

He drags himself away, chest heaving, but grins when he sees Sylvain. He is panting equally as hard, cheeks alight with a blush, eyes unfocused as he clearly tries to work out what brought on this sudden change in demeanour. 

_You_ , Felix thinks but does not say, you and your stupid enthusiasm, your focus and happiness at small things. _How could I not want you?_

Granted, he really can’t believe he’s already half hard, but still, he doesn’t care at this moment. For a plan has hatched in his mind, made solid by the dazed reaction from one very confusing kiss. 

“Sit on the bed,” Felix says, then leans up and kisses Sylvain once more. 

He knows it’s an antithesis to his words, but kissing Sylvain when he’s this turned on is always a necessity. Their mouths open, and it’s Felix’s turns to make a gasp now at just how warm and wet it is, this kiss which is rapidly unravelling him. He traces his tongue around Sylvain’s, feels a shudder from his body with every well placed lick and motion. 

He steps forward, effectively bumping into Sylvain who doesn’t move for a second, still caught up in the clash of their mouths, until his mind jogs into place and he starts backing up. Felix rewards him by catching his lip in his teeth, pulling on it ever so slightly as Sylvain’s legs hit the bed. 

“Ouch, don’t bite,” Sylvain whines, but smiles, the blood swelling in the bruised section and Felix takes a hand away from Sylvan’s hair to trace it, feeling the accelerated breathing hit the pads of his fingers as he does. 

Sylvain sits slowly, eyes still on Felix, who hands fall away as he does. Sylvain smiles, and Felix just takes him in for a second. Hair mussed up by Felix’s hands, smile wide and anticipatory, a certain gleam in his eye as if he has a plan, a secret he cannot yet tell. But Felix smiles himself, as Sylvain’s hands come to gently rub at his hips. Sylvain thinks he’ll fall into his lap, not without reason, as they do often start that way. 

But the pulse in his ears and the now brimming want he has goes in a different direction. It is also insanely satisfactory to watch Sylvain’s breathing stutter and eyes go wide as Felix knocks away his hands and lowers himself to the floor. 

“Felix…” Sylvain almost breaths out as Felix stares up, hands braced against Sylvain’s thighs. 

“Yes?” he asks, not unkindly, as this is a choice not a demand, and Sylvain exhales shakily, hand coming to muss with his own hair. 

“Where did this all come from,” he says with a laugh, which turns to air as Felix drags his hands up high towards the waistband of his jeans, gaining a small sense of satisfaction when his legs part, falling open gradually and allowing him to sit between. 

“I want you,” is all he says, too focused on the moment in hand to come up with any pretty words. 

Sylvain’s mouth actually drops at this, and Felix smiles, despite the blush that climbs across towards his ears. It gives him even more drive and purpose to this situation; Sylvain who is so masterful at creating sentiments and compliments, becoming flustered when such directness is sent in his direction. 

“Y-you have me,” he says, then almost squeezes his eyes shut in what is probably embarrassment. Felix laughs before surging upwards, momentarily caught up in care and affection, purpose momentarily put aside for a sweeter kiss. 

Although it doesn’t stay so for long, as Felix is pressing into Sylvain’s crotch, and he angles for friction within a couple of accidental brushes against him. Felix breaks the kiss, and grins. 

“Yes. Right where I want you,” he says, right against Sylvain’s lips, not touching but giving the words right against him, as his hands weave down between them. 

“Felix…” Sylvain murmurs, again not kissing him as his hands fumble to undo the buttons, caressing against skin with the pads of his fingers, almost stretching and soothing as they come undone. 

There’s a moment of scrabbling as Sylvain has to canter upwards to remove his trousers, Felix feeling himself strain against his own, pushing it aside in favour of what’s to come. 

This isn’t the first time they’ve done this, but it’s still early enough Felix can count the number of times he’s had Sylvain’s cock in his mouth. It doesn’t quite give him the same trepidation as the first time, but it’s still a learning process, an exploration this early in their relationship in working out what each other likes.

And apparently today, Felix is discovering all types of things about himself, as he looks up at Sylvain, dead in the eyes and says. “Watch me.”

That’s where his bravado ends though, for he doesn’t have the ability to maintain eye contact enough for a response, but instead drags his nails down Sylvain’s thighs, not enough to leave marks but enough to feel each indent, causing Sylvain to spread his legs further so he lets Felix in. 

He can feel the muscles tremble under his fingers and it helps, appealing to this overwhelming need to do something, and he has to restrain himself from going straight for the finish. Instead, he lowers his mouth to Sylvain’s inner thighs, kissing upwards toward where his boxers begin. 

The reaction is instantaneous. Sylvain makes a guttural sound that causes Felix to clench his fingers, gripping tighter so he can kiss and lick his way upwards. Sylvain squirms, and the sounds return, Felix feeling them go straight to his own cock, for Sylvain is incredibly sensitive here, and he has to exploit it with the mood he’s in. 

Sylvain moans, loud and unabashed as Felix sucks a hickey as high as the boxers will allow him to. He pulls back, hands soothing and circling but also making the situation more intolerable with how close they dance to where Sylvain wants them to be. 

“Tease,” his voice echoes, already a little broken as Felix stares at the rapidly forming bruise on skin. He glances up, and Sylvain is leaning forward, smile the very definition of flirtatious, even though Felix can see him straining through his boxers, hint of a darker patch appearing. 

So he moves upwards, slowly, hands remaining on Sylvain’s legs, drawing closer. And Sylvain watches. Focused on every motion and Felix’s mouth goes dry with want, need, anticipation. He pauses just before Sylvain’s mouth saying nothing. Sylvain’s legs strain under his, clearly wanting to move, to agin, but Felix just stares and feels, letting the cresting tide of these feelings wash over. 

Sylvain huffs. “Really, such a tease,” he says, but it’s affectionate, accompanied by his hand reaching up to cup the side of Felix’s face, thumb moving over the skin under his eye as if he hasn’t just been marking up the inside of his thighs as a promise. 

“Not a tease if I have the follow through,” Felix remarks, then, somewhat grudgingly moves out of the sweet caress, and without further ado, pulls back the waistband of Sylvain’s underwear. 

He’s hard, leaking a small amount, and that yearning returns as Felix grins back at Sylvain, who gulps at the swiftness of the tone. 

“Keep watching,” he says, before giving in; kneeling down and taking as much of Sylvain into his mouth as possible in one go. 

Sylvain clearly tries not to buck up, only doing so slightly with the cry which echoes, and Felix clamps down on his hips to stop him from choking him, as Felix may be learning more of this, but he’s not prepared to have Sylvain start ramming his throat. Not right this second, anyway. 

“Sorry, shit, sorry Felix, ah your _mouth_ ,” 

The compliments are disarming, as is the gentle tangle of Sylvain’s hands in his hair, and Felix is so not used to this combination of sweet and sexy. So he focuses on what’s in his mouth, sliding up Sylvain until the tip is balanced on his tongue, glancing up through his eyelashes. 

Which is most certainly a mistake as Sylvain looks a perfect mess of half undone and just holding back, mouth slightly parted, high flush on his cheeks and eyes blow wide, groaning as their looks are exchanged. 

“Felix, please, sweetheart I’m watching, keep going,” he stutters out, and Felix, despite it or perhaps because of it all, complies. 

He tongues the slit, bitterness souring through his overfilled mouth, before sinking down once more, one hand moving off Sylvain’s hip to grasp the parts he cannot take in, allowing saliva to drip down in an obscene way which would normally make him uncomfortable, but now he doesn’t care. In fact, it’s a thrill when Sylvain pulses in his mouth, the slide of his grip helping give more of what he wants. 

It’s easier to ignore his own arousal when thinking of what he’s doing, but as Sylvain becomes closer he can’t help but palm himself just once. But the sudden touch after so long of feeling this on edge is too much to keep to himself and he moans, stuttering in his rhythm. 

But apparently Sylvain has no problem with that, as he throws his head back with a groan, Felix being able to tell by the slight thunk of his head hitting the wall. He focuses then, for he can tell by the way Sylvain’s hips move, the way his hands slightly pull at Felix’s hair that he’s getting closer. 

He manoveres his hand around Sylvain’s boxers, until he can cup his balls, the touch causing Sylvain to gasp as Felix moves his head to ensure his tongue pushes against the vein on the underside. He's rewarded by Sylvain hunching over, his cock pulsing again as Felix’s grip and mouth close around. 

“F-Felix close, I’m close—” he manages, cutting off with a moan and Felix lifts his mouth off just in time, hand jerking upwards just once before Sylvain comes, groaning deeply and painting his own shirt white in the process. 

Felix works him through, stopping once Sylvain’s eyes flutter shut before removing his hand. He barely has a chance to look for something to wipe it down with before he's being pulled into Sylvain’s arms, the kiss he’s greeted with sweet and languid, inviting even as his own pulse thrums with barely sated interest. 

“I’m not sure where that came from but… I’m not complaining,” Sylvain says, voice taking on that sated, almost mesmerizingly sleepy tone that follows sex. 

“Good, now get off me, I need to clean up,” Felix says, feeling acutely aware how gross and sticky his hand is. 

All at once, Sylvain’s mood transforms to energised, and Felix has barely any warning before he’s pinned, messy hand and all, to the bed. 

“Now why would you, when you’re going to get even filthier?” Sylvain says, before diving down and kissing him. 

Felix forgets how this all started in favour of better things. 

* * *

He recalls though, an ice bucket thrown over him in full force, a week or so later when Felix is studying at Sylvain’s place. He’s unsure exactly why he’s there and not in the library or his dorm, but apparently Sylvain has this ability to make him cave in the very way he asks for Felix’s attention, even if it’s just to sit next to him while they study. 

He’s trying to translate a particularly dull UN report when Sylvain’s flatmate starts explaining the issue with her literature essay in increasingly worried tones. Felix mostly tunes her out, although her tone gets higher and higher as she panics, as so it’s increasingly difficult to focus. 

Bernadetta is close to tears by the end and Felix finds himself staring unhelpfully as Sylvain listens with a sympathetic expression, mostly as he hates seeing people cry yet never has the right words to help them, and in this case, he’s completely lost. He has no idea how to help her, and can’t see how Sylvain would, either. 

“Have you thought about linking it to the creation of the printing press? It’s actually pretty interesting, if you take into account the role of the Church…” 

It slams into Felix without warning, his blood draining downwards while his pulse spikes as Sylvain’s face takes on an animated tone, eyes lighting with excitement. His hands move, marking out ideas and points but Felix imagines them on him: in his hair as he’s dragged in for a kiss, pinning his hips in place as he grinds down on Sylvian’s lap, working them both up as Sylvain’s fingers slide into his mouth—

He has to get up and leave the table, inhaling deeply and not caring if he looks rude. He’s already half hard just from his own imagination, spurred on by Sylvain talking about the printing press. 

He marches into Sylvain’s room and throws himself down on the bed without care. Strangely, being surrounded by the scent of his boyfriend calms the raging flow of want rather than increases it; he associates this more with comfort than excitement; probably, he thinks with a slight annoyance at himself, because he wears Sylvain’s hoodies whenever he has a bad day. 

He rolls over and stares at the blank wall while he calms down. So. He has a thing for Sylvain being… smart. Or talking about his niche interests. Felix groans and covers his eyes. That’s weird. Not the weirdest thing he could like, but it’s still… hard to explain. And also clearly inconvenient, as proven just now. 

“Felix?” 

He turns over as Sylvain peers around the door, smiling when he sees him in the bed. 

“Sorry, I guess we kinda took over there,” he says, coming in and sitting down beside him. 

Felix sits up and shrugs. “It’s fine. Bernadetta needed help. Plus you… seemed to be enjoying the talk,” he adds slowly and Sylvain’s expression turns bashful. 

“Yeah, her course is really interesting, I always liked Lit,” he says. 

“You know a lot of random things,” Felix says, and Sylvain’s face shuts down a little, and Felix moves before thinking, gripping his hand. 

“I like it,” he blurts out, which is an understatement, to be sure, but it has the desired effect. Sylvain returns his gaze, a thin spark of hope now in his eyes. 

“I guess I just remember a lot of things I read. And if I like something, I get kinda caught up in it,” he says, and with the last word, his smirk forms and he leans closer, Felix raising his eyebrows at the change of tone. 

“Really?” he draws out, staying still and letting Sylvain come to him, which he does, bracing on his arms to gain enough ground to kiss Felix, just a short and sweet touch, before moving back enough to touch their foreheads together. 

“Yeah. I do.” 

* * *

Felix decides not to share his discovery. Not completely anyway, although sometimes he thinks Sylvain may have an inkling after they watch a documentary on aircraft where Sylvain gives an account of how you could fashion a basic craft from most things in his flat and ten minutes later Sylvain has him moaning on the sofa, holding him under him while he grips both their cocks together until Felix is spilling between them. 

The clean up and embarrassment of that is enough for Felix to swear blind they are never doing that again, but Sylvain gives him a look that says otherwise. He really needs to control his urges. 

It’s Annette, who lives in his dorm, who brings up the competition at lunchtime while they get coffee. 

“How can you make maths competitive?” Felix asks, who dropped maths as soon as he was able, while Annette’s music degree means she needs it fairly often. 

“Solving complex formulas under time pressure, calculating faster than the other team. It’s fun!” she says, and Sylvain nods. 

“Although this tiny fury broke the marker last time in frustration,” he says and Annette glares at him.

“One time, and you bring it up forever,” she says with a pout. 

“He does that,” Felix says, and Sylvain smiles. 

“But yeah, it’s fun. You can watch, if you...want to? It’s in the main hall on Thursday,” he says, and Felix hates that there’s still that hesitancy, as if he isn’t already so gone he’s already made up his mind to drop everything in order to watch his boyfriend do maths he most certainly won’t understand. 

He agrees, so on Thursday evening he makes his way to the main hall, meeting Sylvain out front, who waves when Felix almost walks past him, not recognising him until he’s nearer. Which is for good reason, as Sylvain is wearing glasses. A large pair, circular with a thin dark red frame that are probably highly fashionable if Felix had any clue about glasses. 

What he does know is they look good. Really good. 

“Didn’t recognise you,” he says as Sylvain bends down to kiss his cheek, and stands with a laugh. 

“Oh yeah, I don’t need them often, but I find looking at an interactive board for over an hour makes my head ache,” he says, shrugging and taking Felix’s hand as they walk into the hall. 

It’s less than half full, which Felix isn’t surprised by, and Sylvain leads him through the chairs to a group near the front, who look up when he arrives. Annette stands and launches herself into a hug, and Felix catches her with a laugh. 

“I’m nervous,” she says, staring up at him and he nods sympathetically, and there’s a heavy sigh from behind. Annette relunantly turns and her girlfriend, Lysithia looks up from the wad of flashcards. 

“We’ll be fine, Annie. You always get nervous and you always solve everything well. Just don’t break anything,” she adds, before giving Felix a barely perceptible nod and looking back at her cards. 

“One time!” Annette cries, then almost goes flying as she trips over her own chair, both Felix and Lysithea steadying her. 

Sylvain shows him Linhardt, who is apparently power napping in the corner in preparation, and is introduced to his best friend Caspar, who is cheering him on while his boyfriend is out of town. 

“I don’t know anything about Math,” Caspar admits, as Lysithea shakes Lin awake and the four start gathering their things. 

Felix snorts. “I barely passed,” he says and Caspar looks relieved that at least he won’t be the only one who has no idea what’s happening. 

“Hey, we’re on in ten so we’re going to… well, Annette might throw up and Lysithea is just talking in calculations now and Lin’s half asleep so… I’m gonna actually put my bag away,” Sylvain says with a laugh, actually not seeming that nervous. 

“You’ll be great,” Felix says, and stands so he can kiss Sylvain, glasses and all. 

It’s probably a little too fierce, but he wants to show support and apparently Sylvain thinks he’s kiss powered as he is unlocking Felix’s mouth into a kiss that’s almost too deep and long for the public, Caspar actually whistling in the background. 

Felix pushes Sylvain towards the steps and he laughs, readjusting his glasses as he goes, and that sends Felix gulping, almost having to readjust himself in response. 

He isn’t the best at conversing with strangers, but turns out Caspar can talk for two of them, and once Felix mentions he runs, they actually manage to have a decent chat about fitness. But before too long, the stage lights up with the two teams beginning their mathematics competition. 

It’s not what Felix expects. It’s, entirely, in one way, mortifying; Caspar is a one-man cheer-leading team who screams a riot with every correct answer by their team. Annette stumbles over her first go, but apparently that seems to fuel her, for she starts a winning streak of solving formulas in a time Felix is genuinely stunned at, especially as her handwriting is so neat. 

He thinks he hears Lysithea state she ‘doesn’t have time for this’ as she produces an answer that’s more letters than numbers, and Felix could swear at one point Linhardt sleeps through his question and still manages to find the correct answer, yawning all the while. 

Then of course, there’s Sylvain. Felix can barely keep his eyes off him if he’s honest. He answers all questions timely, with a flair of the dramatic which Felix is slightly fond of, even though it also makes him want to knock his head against the wall. He actually winks at a judge when he answers a question barely seconds after finishing, and Felix would be fed up with him for it except…

He’s having fun. Clearly enjoying the thrill of the challenge and being on stage, moments of hesitation when he’s concentrating on what’s coming, when his brow furrows and occasionally moves his hands back behind his head, a tell of slight nerves.

It’s amazing to watch. Sylvain is just on a knowledge level he knows he’ll never quite grasp. But it changes about twenty minutes in where Sylvain is creating some sort of chart against the other team, a huge design that he scribbles across the board, finishing with the number 18.5, twirling around and looking for all that Felix can gather, straight at him. 

He’s caught in that fire of a gaze, the epicentre of Sylvain’s complete focus and understanding of something so fundamentally brilliant, that Felix cannot take a single breath. Then, he’s called the victor, his team cheer, and Sylvain smiles, serene and pleased, before sweeping his hair out of his eyes, catching on the rim of his glasses as he does. 

And Felix _needs._

Needs Sylvain now, right this second, backstage for all he cares, but he knows he can’t. Which just makes it a thousand times worse because he won’t be able to even go near Sylvain for another forty minutes. So he just stews in his own frustration as the night goes on, varying between genuinely engaged and lost in the boiling of his own blood when Sylvain bites his lip in focus or recites correct answers before the question has even finished. 

It is fun. Felix just wishes he wasn’t half hard and uncomfortable while watching.

Caspar grabs onto his arm as the last question is announced, the points, close but their team in the lead. Each team confers, then with an air of confidence Felix is impressed by, Lysithea steps forward as the representative of their team. She puts together a model of multiplication that has Felix and Casper exchanging bemused looks, but it doesn’t matter for whatever she’s done, she’s correct. 

They’ve won. Felix smiles and claps, watching his boyfriend lift Annette high up in celebration while Casper screams the house down. They get stared at, by everyone but it is worth it for the happiness of everyone’s faces as they rejoin, having had their photos taken with a trophy, Team Captain Lysithea holding it proudly. 

“That was awesome!” Caspar booms, and then launches into a play by play of Lin’s awesome ‘swirly lines’ which his friend nods along too indulgently, while Lysithea seems scandalised their math is reduced to that. 

“What did you think?” Sylvain says, practically bouncing over to Felix with an energy that must be half nerves, half adrenaline, and there is really only one answer he can give. So he draws forward slowly, looking up at Sylvain as he reaches up to tangle his fingers in the back of Sylvain’s hair, a clear indicator of what he wants yet not making the final move. 

Sylvain does though. Bending, reaching for Felix in what he probably imagined would be a sweet kiss but Felix opens up in an instant, deepening, pouring the last hour into the movement, Sylvain hitching in his arms and breath mingling. He doesn’t allow it to last thought, pulling back with a sound of something wet and clinging, and Sylvain is almost as red as hair, Felix grinning at the result. 

“Ew. Go home, now,” Lysithea says and Felix turns to glare. 

Annette laughs. “I’m too tired to celebrate now, my head hurts. We should go out on the weekend when Byleth is back,” she says, and Lin nods, looking pleased but tired. 

They say their goodbyes and Sylvain intertwines their hands as Felix starts marching across campus. 

“Where exactly are you taking me?” Sylvain says with a chuckle that is far too light-hearted for how wound up Felix feels. So he spins and grabs Sylvain by the collar, who stumbles at the force, eyes going wide. 

“My dorm, your place, an alley for all I care right now,” he half grows and Sylvain’s mouth falls open. 

“W-whoa okay, err, let’s go to my place,” Sylvain says, stumbling in that adorable way which makes Felix just need to kiss him again, although it’s more of a grab and bite this time, pulling Sylvain’s lip between his teeth as they part. 

“What’s gotten into you?” Sylvain mutters, foreheads close and his hand carding down Felix’s back, soothing even through the layers of clothing. 

Felix hesitates, isn’t sure if he wants to explain or how the words to explain this operate, but he’s so far into this, he needs to express something. 

“Just you. Tonight doing… whatever the fuck that all was,” he says and Sylvain pulls away, looking confused. 

“Wait, you’re riled up over watching a math competition?” he says and Felix pulls completely away, arms folding over his chest. 

“No, you idiot, over you. I don’t even know what the hell all of that was,” he hisses, aware there are still people around. 

Sylvain holds his hands up, teasing gone and a smile forming. He puts them down slowly, then offers a hand to Felix. 

“Come home with me?” he asks, sweetness and light, and Felix takes the hand with a sigh, some of that pent up energy vanished in his own embarrassment. But Sylvain pulls him close as they walk, which makes travelling ten times harder but is a sweet gesture. 

It’s not far. Felix’s place would have been closer, but Sylvain’s is more comfortable, what with it being an actual house. Bernadetta is watching a show, and gives them a wave as they pass, straight up the stairs and into Sylvain’s room. 

“Sooo,” he drawls, and Felix braces himself for aggravation with the tone of voice, “You think I’m hot when I do equations,” he says and Felix huffs, facing Sylvain. 

He looks at him, tries to see and understand fully what’s the best way to approach this. Sylvain is teasing but there is a curiosity to it, a wonderment that is so much better than the doubt he’d seen in the early parts of their relationship. And this makes him bold, makes him stepforward into Sylvain’s space, who is waiting, smirk forming. 

“I think you’re hot when you’re smart, Sylvain,” he says, leaning close but not touching, and he sees the moment the control slips and Felix has him exactly where he wants him; a little flustered, a little out of the driving seat so he can take over. 

Felix isn’t great with words but Sylvain is apparently responding to them, so he tries his best to keep going. 

“When you focus, when you bite down on your lip as you concentrate… I want you. When you light up like you do as you talk about your interests, you’re hotter than when you use those ridiculous lines, Sylvain,” he says, now against Sylvain’s lips, just a shade away from a kiss. 

Sylvain exhales, breath on Felix’s skin, and there are no more words he can use as Sylvain ducks down to press their mouths together. The heat of before is back, this time shared in instantaneous gasps and sighs, Felix clawing his hands into Sylvain’s hair as he’s finally, finally able to let go. 

His body returns to his previous state and he aches for more than promise and prelude. Sylvain though seems to be swiftly ramping up to the same level, for he lifts Felix up by his thighs, a scramble as Felix will not stop kissing to be moved, but he manages to hike his legs around Sylvain’s middle enough so they can fall onto the bed. 

“Watch my head,” Felix says as he bounces almost into the wall, Sylvain hovering over him with a grin. 

“As if I’d let you smash into the wall,” Sylvain says with a justified roll of his eyes, but Felix doesn’t give him the time to be smug, hands roaming to the hem of his shirt. 

“Off,” is all he demands and Sylvain obliges, back to bearing over him, arms straining against part of his body weight, chest flexing, and Felix’s eyes are glued to skin, tongue coming to lick his lips, which Sylvain’s gaze follows. 

Felix sits up, then draws Sylvain in, kissing him once then moving to his neck, the vibrations of his voice melding unto the taste of his skin as Felix makes tiny marks that will exist for only a few moments, his own indents as Sylvain’s noises run through his ears. 

“Hmm, okay enough mauling me and take your shirt off,” Sylvain says, and Felix sighs, pulling back and whipping his own shirt off his head without preamble. Sylvain chuckles as he does. 

“One day, I’ll manage to get you to slow down and let me watch you properly,” he says, leaning forward to kiss Felix sweetly, a strange change in atmosphere as Felix feels heat rise in his face. That’s not something he’s ever thought anyone would want...but it’s worth storing for another time. 

Now, he just wants Sylvain. 

The mood must be clear because Sylvain eases him down onto the bed, his weight a blessing, a balm that both heats and soothes, every touch point electrically fizzing so harshly Felix cannot keep up with each ignition. 

He gasps and pushes up, Sylvain groaning as their crotches brush, mouth locking onto Felix’s as he fights upwards, wanting more, more, more; more Sylvian, more pressure, more of everything this moment has. 

“Steady, sweetheart,” Sylvian tries, breaking free and grinning while Felix makes a sound of frustration. 

“I have been waiting—” 

“Hush okay, let’s get these off you then,” he says, reaching for Felix’s belt with a wink which makes him want to slam his boyfriend up against the nearest wall. 

But that would involve all of stopping, and Felix doesn’t think a meteor would break him away from Sylvain now, as he helps him out his jeans and pants, the temperature change of his heated skin making him shiver. 

He starts barely a second later when Sylvain’s mouth ghosts along his leg, just above the knee, pushing his legs apart as he moves between them. The pressure of his lips increases as he moves higher, the scratch of his stubble scoring friction which has Felix’s hand flying into his hair as he moans, on edge already. 

Sylvain doesn’t stop though, just grazes his teeth against the inside of Felix’s thighs, coursing upwards until he’s just where Felix needs him to be, his legs starting to shake as pre-come pools and drips in anticipation. 

So of course Felix pulls up and tries to sit, panting hard, when Sylvain leans forward hand on his chest. 

“One second. My god baby, you’re so ready,” he says with a grin and Felix glares. 

“Do not call me that,” he says, and Sylvain turns back, half sitting up, an apologetic look crossing his face. 

Felix can’t explain why he hates that nickname, it’s always bothered him, and Sylvain shuffles closer, hand rummaging through his bedside table draw, murmuring nonsense apologies into Felix’s air, pressing kisses absently in his wake. 

He should have known it’s a distraction, and yet when Sylvain circles a hand around his cock the shock is so much his back bends. He knows Sylvain is laughing against his neck, but Felix doesn’t care, just sinks into the slow rhythm, hips rising slightly to the upwards and downwards, eyes closing. 

He’s already building, not close but not far, and he opens his eyes with a gasp when Sylvain stops. 

“Lay down again,” is all that’s murmured against his temple, and Felix has no will yet to comply, inhaling shakily, mouth dry as Sylvain stands, removing his own pants and underwear almost too quickly for Felix to see. 

He has the audacity to wink down at Felix, before his hand falls to his own cock, head thrown back and mouth gaping in a show that has Felix sitting up swiftly, only to be pushed back down as Sylvain climbs over. 

“I’m here, but you gotta lay down, Felix,” he says, and Felix cannot use words anymore, has forgotten language. He lets Sylvain reshape them until he’s back between his legs, leaning over with his hands spreading his thighs wide. 

He loves the strain and stretch, the look in Sylvain’s eyes as he coats his fingers in lube, staring up at Felix briefly before he begins. The first touch to his entrance is a relief, and the slide has him gasping at the ceiling, hands once again going to his hair in the need for grounding. 

“So wound up, Felix, you look so good. I can’t believe I can get you like this,” Sylvain mutters, more to himself, Felix thinks, as he pumps slowly in and out, Felix managing to swallow hard to clear his throat. 

“You always do—ah, Sylvain, yes!” he cries as a second finger is added and he knows he’s not going to last much longer. 

There’s a groan and a shift in pace and Felix manages to pull himself up a little to see Sylvain gripping himself, hand slick and pumping, which causes another twitch in Felix’s own cock. 

Sylvain’s hair has fallen across his eyes in a look which should be only created by hours of effort and not a roll in the sheets, and he smiles that lopsided, real smile that’s so bright and full of care. Felix smiles back, momentarily just caught in affection, lost on what he thinks will soon be love. 

That is until Sylvain shifts and takes Felix deep into his mouth. 

A shout is the only word for what rises from his throat, hands gripping the sheets so hard his fingers ache. Any sense of a slow build up is thrown away as the dual heat of Sylvain’s mouth combined with his fingers scissoring and glancing over Felix’s prostate are sending him spiralling forward. 

It’s too much, too wild and intense, so much he turns his head away, as if to shield himself from just how stimulated every nerve feels. It almost hurts, almost makes him want to call stop, but the noises instead are demands for ‘more’ and ‘keep going,’ up and up up and up until he’s pushing at Sylvain’s head, pulling off just in time to narrowly miss his face being hit by come. 

Felix gasps his way off the precipice, Sylvain’s rhythm becoming softer, more leisurely as the aftershocks settle in. His cheek hurts where he’s been biting it, his hands ache from their grabbing and his vision is spotted with grey. 

He flinches a little when Sylvain's hand brushes his cheek, any touch too much, but static clears and he manages a tired smile before leaning back carefully into the touch. 

“Too smart for your own good,” he whispers, and Sylvain’s laugh is birdsong, wind-chimes, all those horrible cliches he’s starting to understand. 

He rests their foreheads together, Felix aware he has precious few minutes before he’s overcome with just how disgusting he is. So he kisses Sylvain, soft and sweet, a hope that he’s starting to realise just how wonderful that stupidly clever brain of his is. 

**Author's Note:**

> I'm on [Twitter](http://www.twitter.com/EnlacingL/) here, come talk to me about FE3H


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